'Supermoon' Science: Biggest Full Moon of 2013 Explained

Skywatcher Roberto Porto took this photo of the biggest full moon of 2012, a so-called supermoon, in Costa Adeje, Tenerife, Spain, on May 5, 2012.

Roberto Porto

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2012SupermoonImagesfromOurReaders:Photos

View Caption+#1: May 7, 2012 --

The biggest full moon of the year, a "supermoon," could be seen in the night sky on Saturday.
We asked our Tumblr and Twitter followers to send in pictures of the supermoon from around the world.
According to Space.com, "Because of a fluke of orbital timing, the full moon of May peaked late Saturday just as the moon was passing its perigee, the closest point to Earth of its orbit. The result was the biggest full moon of the year, which NASA and other scientists nicknamed the supermoon of 2012."
The following pictures show an array of places and settings for the picturesque moon.
Here, the supermoon is seen from El Salvador.

View Caption+#2: The perigee moon, as seen from Spain.

NEWS: Spectacular 'Supermoon' Wows Spectators

View Caption+#3: The moon, seen over Brawley, Calif.

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From Tumblr iamloy: "Here's a close up picture of the supermoon or perigee moon we have tonight. The moon is the brightest tonight out of the whole year. This picture was taken in an island called Guam."
Camera : Canon Rebel T3i
Lens : 18-55mm f/3.5-5.6
F-Stop : f/5
Exposure Time : 20 seconds

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The moon perigee as seen from California through a 4.5" Dobsonian telescope.
from sagan-naut Tumblr

View Caption+#6: The supermoon over Reno, Nev.

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This supermoon "teaser" was taken Aurora, Colo. with a Canon PowerShot SX30 IS.
PHOTOS: Top Ten DiscoveryNews Tumblr Posts of 2011

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This perspective was taken from Kit Carson Park in Taos, N.M., May 5, 2012.

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This shot of the supermoon, with a halo, was taken by Jason Major in Dallas, Texas.

Science governs the appearance of the largest full moon of the year, and this weekend you can check out the amazing lunar sight for yourself.

On Sunday (June 23), the moon will be at its closest point to Earth — called perigee. This relatively close brush will happen as the moon enters its fullest phase, creating the cosmic coincidence known as the supermoon. At its fullest and closest, the moon will appear about 12 percent larger in the sky. [Amazing Supermoon Photos of 2012]

"It doesn't matter where you are, the full moon you're seeing will be the biggest for 2013," Michelle Thaller, the assistant director of science at NASA's Goddard Space Flight Center said. "… That 12 percent size different can mean as much as a 30 percent change in the brightness, so this will be a particularly bright supermoon."

How to see the supermoon

Weather permitting, everybody should be able to see the supermoon. The moon will be rising from the east right around sunset, Thaller said. It will appear huge and low on the horizon before rising brightly into the sky for the night. Saturday and Sunday should both be ideal viewing opportunities.

Supermoons occur about once annually, and this year, the supermoon is closer than it has been in a little while, Thaller said.

The distance from the Earth to the moon varies along the rocky satellite's elliptical orbit. Perigee differs from month to month, so sometimes the supermoon is a little closer or further away, Thaller said.

"The closest the moon gets can actually vary much as much as the diameter of the Earth," Thaller said. "That seems like a pretty big number, but the moon is actually 30 times the diameter of the Earth away from us. If you line up 30 Earths, that's about the average distance of the moon away, but as it swings a little bit closer to us, that distance can vary."

The sun can be to blame for the difference in distance. In the winter, when the Earth is closest to the sun, a supermoon could be even closer and more stunning, Thaller said. The strength of the sun's gravity pulls both the moon and the Earth towards it slightly, making the moon dip closer to the planet.

Science from a supermoon

Although it might be a brilliant skywatching opportunity, not a lot of scientific research comes from the supermoon. Scientists prefer to study the moon from a closer vantage point, Thaller said.

"The supermoon for is a fun chance to talk about the changes in the sky observing the universe," Thaller told SPACE.com. "As scientists, we like to observe the moon a little bit closer up and right now we have LRO, the Lunar Reconnaissance Orbiter, a spacecraft actually orbiting the moon. We're taking these incredible high resolution pictures of the entire lunar surface."